The 1.320 micron Nd-YAG laser. Experimental study of a new wavelength adapted to neurosurgery

The authors present a new laser wavelength for neurosurgery: the 1.32 micron Nd-YAG laser. Schematically, it combines the advantages of both the 1.06 micron Nd-YAG laser and the CO2 laser. As for nervous tissue it has the same physico-thermal properties as the CO2 laser: an important absorption and little thermal diffusion. Like the 1.06 Nd-YAG laser, the 1.32 Nd-YAG has very good maneuverability, because its beam is conducted through optical fibers. Experimental studies have been made on rats. They consisted of comparison between the thermal effects and the consequent histological lesions of three lasers: 1.32 micron Nd-YAG, 1.06 micron Nd-YAG, CO2. 145 impacts on the cortex of 45 rats have been studied. Each shot was registered with an infrared camera, measuring the cortex surface temperature around the impact. The signals were digitalized; they allowed us to obtain a numerical image and the profile of temperature for each shot, as well as the development of temperature of each point of the profile. These results have been correlated with the histological data. It appears that for equivalent efficient outputs, the cortical lesions, 8 days after the shots, were similar for the 1.32 Nd-YAG laser and the CO2 laser. For instance, the depth of the coagulation necrosis varied from 200 to 250 microns after CO2 laser impacts (P = 3W; t = 0 05s; Fluence = 5 Joules/cm2), and from 210 to 260 microns after 1.32 Nd-YAG laser impacts (P = 5-14W; t = 0.4s; F = 50-170 J/cm2).(ABSTRACT TRUNCATED AT 250 WORDS)     

Preliminary evaluation of a pulsed 2.15-micron laser system for fiberoptic endoscopic surgery

There is a need for lasers that are compatible with fiberoptic endoscopes and that provide greater cutting precision than currently can be produced by the widely used Nd:YAG (1.06 micron) laser. Recently available lasers that operate in the 2-micron region fill this need. This laser light energy can be transmitted by low OH- silica fibers and has much less tissue penetration than radiation at 1.06 micron. We have been evaluating a prototype solid state laser system that produces pulses of 2.15 microns light that is delivered by a silica based fiberoptic delivery system with negligible transmission losses. This system is based on a thulium-holmium-chromium doped YAG (Tm-Ho-Cr: YAG) rod that lases at 2.15 micron. The laser does not require cryogenic cooling, toxic gases, or custom utilities and should be practical in a clinical environment. In vivo animal testing of this laser confirms that it provides greater ablating precision than does the Nd:YAG laser at 1.06 micron.     

Imaging the spinal cord in scoliosis in magnetic resonance tomography using the 3D Fourier procedure

Recent progress in MR-imaging allows to acquire an entire volume using 3D-Fourier-processing, resulting in an isotope spatial resolution with a voxel-size of about one cubic millimeter. Acquisition time for a matrix of 256 x 256 x 128 amounts to less than 15 minutes, if gradient-echo-sequences are applied (FLASH/FISP). The information contained in such a huge number of data is retrieved with the aid of a special rapid data processing system. Using 3D-Fourier analyses, Spinal cord is imaged very clearly even in cases of extreme kyphoscoliosis. The cord is demonstrated by arbitrary, even curved one Millimeter slices. In addition to that the acquisition of data takes only 15 minutes, which is definitely more rapid than 2D-Fourier. Details can be figured out in a very high precision. This allows to distinguish details such as vessels, small masses and nerve roots. Furthermore the signal-to-noise-ratio of 3D-sequences is higher than in multi-slice-technique. A decisive advantage is the possibility to compute curved planes in post processing of the 3D-data-sets.     

Evaluation of the effect of shape on a contemporary CAD system

The TracerCAD system is one of the leading prosthetic CAD systems in the world and is increasingly used in clinics to replace traditional methods of residual limb shape capture. Accurate dimensional capture of the residuum is arguably the most important process in the production of a prosthetic socket. TracerCAD system accuracy has previously been tested on a cylindrical model but not a trans-tibial shape. Residual limbs are irregular in shape therefore it is important to assess if shape has an effect on the accuracy of data collected when using TracerCAD. The objective of this study is to investigate the accuracy of the TracerCAD system in measuring a model of a trans-tibial stump of known dimensions and volume. A model of a trans-tibial stump was produced and filled with plaster and measured using a data acquisition system with an accuracy of five micron (0.005 mm). The model was repeatedly traced using the TracerCAD system by an individual user. The mean value of measures taken by the dynamic indicator was calculated and compared to individual and mean values of TracerCAD measurement. Results showed that the TracerCAD measurement was not as consistent on the more complex trans-tibial model as for the cylindrical model.     

The role of pars flaccida in human middle ear sound transmission

The role of the pars flaccida in middle ear sound transmission was studied with the use of twelve otoscopically normal, fresh, human temporal bones. Peak-to-peak umbo displacement in response to a constant sound pressure level at the tympanic membrane was measured with a noncontacting video measuring system capable of repeatable measurements down to 0.2 micron. Measurements were made before and after pars flaccida modifications at 18 frequencies between 100 and 4000 Hz. Four pars flaccida modifications were studied: (1) acoustic insulation of the pars flaccida to the ear canal with a silicone rubber baffle, (2) stiffening the pars flaccida with cyanoacrylate cement, (3) decreasing the tension of the pars flaccida with a nonperforating incision, and (4) perforation of the pars flaccida. All of the modifications (except the perforation) had a minimal effect on umbo displacement; this seems to imply that the pars flaccida has a minor acoustic role in human beings.     

The evaluation of bone remodeling about orthopaedic implants with ultrasound

Total hip arthroplasty causes biomechanical changes in the normal femur, including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Two complementary ultrasonic techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. An ultrasonic wave propagation technique was used to determine elastic properties and a new scanning acoustic microscope (SAM) mapped the acoustic impedance profile of each section. The effects of the implantation of two types of hip prostheses, an uncemented bipolar prosthesis with an Austin-Moore type stem and a cemented Charnley prosthesis, were investigated. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. The SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.     

New Processes for Surface Treatment of Catheters

Abstract: Infection, thrombosis, and stenosis are among the most common complications of blood-contacting catheters and are caused by surface properties of the substrate materials. Ion beam-based processes such as ion implantation and ion beam-assisted deposition affect only the outer micron of the treated material surface; there is little effect on bulk properties. These processes were therefore used on common catheter materials, and their biological properties were evaluated. Ion implantation of materials such as silicone rubber resulted in a less tacky, more wettable surface that demonstrated thrombusresistance in both in vivo and preliminary clinical studies. Ion beam-assisted deposition was used to deposit silverbased coatings, which demonstrated antimicrobial activity in in vitro and clinical studies. Biocompatibility of these processed catheter materials was also demonstrated using simple laboratory studies. These processes, therefore, can be readily applied to blood-contacting catheters to make them thrombus- and infection-resistant.     

Spine needle biopsy simulator using visual and force feedback.

OBJECTIVE: Biopsy with an inserted needle is an important procedure for lesion detection in the spine, but is difficult to perform due to the presence of many critical organs near the spine. This article presents a spine needle biopsy simulator, based on visual and force feedback, which can be used to plan the optimal path of a needle and to practice the procedure without risk. MATERIALS AND METHODS: The simulator is composed of a 3D human model, a visual-feedback component, a force-feedback component, and an evaluation module. The human model is based on 3D CT data. The visual-feedback component provides an oblique section, multiplanar reformatting images, and a volume-rendered image. Of these, the oblique section display is very useful for planning a 3D path for the needle. During simulation, the force-feedback component generates and provides realistic forces acting on the biopsy needle in real time by synchronizing them to visual feedback. After each simulation, the evaluation module provides a performance analysis for the trainee. RESULTS: For an XCT abdomen volume data set of 256 x 256 x 256, the update rate of image rendering due to needle movement is over 25 Hz, with a force-feedback rate of 1 kHz. This performance proved to be good enough for the trainee to learn the relationship between visual and force feedback. CONCLUSIONS: The simulator is useful for the planning of and training in complicated 3D spine needle biopsy procedures. It may be used as an educational tool for beginners, a practice tool to increase expertise, or a test bed for new procedures.     

2微米激光对人前列腺组织汽化比率的体外实验研究

目的 体外观察2μm激光对良性增生前列腺组织的汽化、清除比率,探讨估量经尿道2μm激光前列腺汽化切除术中前列腺组织清除最的方法.方法 经开放手术获取新鲜前列腺组织标本共9个,立即称量质量,模拟经尿道2μm激光前列腺汽化切除术条件下进行体外前列腺汽化切除术,每个腺体均被完全切割至直径小于1.0 cm的碎块.术后立即称量收集到的全部前列腺组织碎块质量,计算出丢失的前列腺组织质量,进一步分别计算出收集到的前列腺组织质量及丢失前列腺组织质量在前列腺腺体标本质量中所占的比例,并对收集到的前列腺组织质鼍与整个腺体质量间的相关性进行分析.结果 相对于前列腺腺体标本质量,收集到的前列腺组织质量所占比例为(34.5±1.5)%,丢失前列腺组织质量所占比例为(65.6±1.5)%.收集到的前列腺组织质量与前列腺腺体标本质量成线性关系.结论 体外模拟经尿道2 μm激光前列腺汽化切除术的条件下.根据所收集到前列腺组织质量可以计算出前列腺组织的汽化、切除比率,并可进一步推知相应的前列腺组织 清除量.     

基于碳纳米管的靶向超声造影剂在肿瘤中的应用进展

纳米级靶向超声造影剂具有无辐射、实时显像及高度靶向性等优点。其中碳纳米管(CNT)具有独特的光学、电学和声学特性及较高的比表面积和良好生物相容性,通过对其进行修饰或改性,可制备出性能优良的复合纳米材料,用于诊断及治疗肿瘤。本研究对基于CNT的靶向超声造影剂在肿瘤中的应用进展进行综述。     

Antimicrobial effects of two anaesthetic agents: dexmedetomidine and midazolam

Some anaesthetic agents are known to inhibit microbial growth. The aim of this in vitro study was to investigate possible antimicrobial effects of two frequently used agents in intensive care units, dexmedetomidine and midazolam. Antimicrobial effect was tested on Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa by broth microdilution method. Midazolam showed inhibitor and bactericidal effect on S. aureus at concentrations 256 mmicrog x ml(-1) and 512/microg x ml(-1) respectively and on E. faecalis at concentrations 128 microg x ml(-1) and 256 microg x ml(-1). Dexmedetomidine demonstrated inhibitor effect on S. aureus, E. coli and P aeruginosa at concentrations 32 microg x ml(-1), 16 microg x ml(-1) and 16 microg x ml(-1) respectively. Midazolam had inhibitor and bactericidal effects on S. aureus and E. faecalis. Dexmedetomidine had only inhibitor effects on S. aureus, E. coli and P aeruginosa. Further studies are needed to determine the antimicrobial mechanisms and clinical applications.     

Intimal thickening in autogenous vein grafts in rabbits: influence of aspirin and dipyridamole.

The effects of three different platelet modifying regimens on the degree of intimal thickening of autogenous vein grafts in rabbits were measured one month after operation. Dipyridamole alone (2 mg/kg/6 h) had little effect on the intimal thickness of these rabbits compared with that of controls (mean (1 SEM) for treated animals: 72.0 (7.9) micron; controls: 63.6 (6.0) micron). High dose acetylsalicylic acid (40 mg/kg/24 h) plus dipyridamole (2 mg/kg/6 h) increased intimal thickening significantly (85.8 (6.0) v 63.6 (6.2) micron; p = 0.05, n = 17). Low dose acetylsalicylic acid (0.5 mg/kg/24 h) plus dipyridamole (2 mg/kg/6 h) also increased intimal thickening (79.0 (6.1) v 63.6 (6.0] micron but not to a significant degree. It has previously been shown in vitro that acetylsalicylic acid increases the area of an exposed subendothelial arterial surface covered by platelets. Such an effect may explain our finding of increased intimal thickening with high dose acetylsalicylic acid plus dipyridamole.     

雷帕霉素对大鼠肝癌的抑制作用及其机制

目的 探讨雷帕霉素对大鼠肝癌抑制作用及其机制.方法 40只大鼠随机等分为雷帕霉素组、对照组,观察雷帕霉素对大鼠经门静脉播散的肝脏复发肿瘤复发率和生存情况影响.应用噻唑蓝(MTT)比色法观察其对walker-256肿瘤细胞增殖影响;应用流式细胞仪观察其对肿瘤细胞周期影响;应用荧光定量聚合酶链反应(PCR)观察其对肿瘤细胞血管内皮生长因子(VEGF)mRNA表达影响.结果 雷帕霉素组荷瘤大鼠荷瘤肝重为(12.5±0.2)g,较对照组(14.4±0.3)g轻,两者差异有统计学意义(P<0.05);雷帕霉素组荷瘤大鼠荷瘤肝重比为(61.3±0.6)x 10-3,较对照组(70.8±1.3)×10-3小,两者差异有统计学意义(P<0.05);雷帕霉素组大鼠肿瘤复发率为90%,对照组为95%,两者差异无统计学意义(P>0.05);雷帕霉素组生存时间为(26.5±2.5)d,对照组为(14.8±2.3)d,两者差异有统计学意义(P<0.05).MTT比色法示雷帕霉素对walker-256肿瘤细胞有抑制作用,IC50为9.60μg/L;细胞周期检测示雷帕霉素组G1/G0期比例为(55.2±0.1)%,较对照组(45.2±0.4)高,两者差异有统计学意义(P<0.05);雷帕霉素组VEGF mRNA表达(4.50±0.13)×10-2较对照组(70.8±1.3)×10-2低,两者差异有统计学意义(P<0.05).结论 雷帕霉素通过抑制肿瘤细胞倍增和减少促肿瘤血管内皮生长因子的表达来延长宿主荷瘤生存时间.     

Presentation of intraosseous vascularization by sequential maceration

Using the example of a knee joint, an injection-maceration technique used to present the pattern of arterial vessels inside and outside the bone is described. Femur and tibia are fixed in a rigid position by central cemented shafts, after synthetic resin has been injected i.a. into preparations of the thigh. The actual maceration of soft tissue is not done as a single process but in several steps. In this way, breaking of fine vessel ends as a result of mechanical overload is avoided. After the soft tissue has been completely removed, the bone surface is coated with resin, while the articular surface is left uncoated. In the final step the three-dimensional structure of the bone surface and the pattern of the periosteal vessels remain unchanged. The method described allows presentation of intraosseous arterial vessels less than 20 micron in diameter. The results that can be obtained are demonstrated using the example of arterial supply of the patella and of the condyles of the femur.     

Plasma-mediated ablation of corneal tissue at 1053 nm using a Nd:YLF oscillator/regenerative amplifier laser.

Plasma-mediated ablations were performed on human donor corneas with a short pulsed Nd:YLF laser system at 1053 nm. The pulses were 60 psec in duration at a repetition rate of 1.0 kHz. The laser beam was oriented perpendicular to the cornea surface. The threshold energy densities for ablation of epithelium, Bowman's membrane and stroma were measured. They were 6.1 +/- 1.8 J/cm2, 21.0 +/- 5.1 J/cm2 and 10.4 +/- 1.8 J/cm2, respectively. The mean rate of tissue removal at the stromal energy density threshold was about 1 micron per pulse. The walls of the laser excisions were smooth with distortions of less than 1 micron. A new quantitative model of plasma-mediated ablation is introduced and found to closely predict the observed results. Based on the promising nature of the experimental data further investigations are planned in the use of a mode locked Nd:YLF laser as an alternative to excimer lasers for refractive corneal surgery.     

Novel approaches to needle tracking and visualisation

The accuracy and reliability of ultrasound are still insufficient to guarantee complete and safe nerve block for all patients. Injection of local anaesthetic close to, but not touching, the nerve is key to outcomes, but the exact relationship between the needle tip and nerve epineurium is difficult to evaluate, even with ultrasound. Ultrasound has insufficient resolution, tissues are difficult to discern due to acoustic impedance and needles are more difficult to see with increased angulation. The limitations of ultrasound have shifted the focus of innovation towards bio-markers that help detect needle tip position by utilising the physical properties of tissues, (e.g. pressure, electrical, optics, acoustic and elastic). Although most are at the laboratory stage and results are as yet only available from phantom or cadaver studies, clinical trials are imminent. For example, fine optical fibres placed within the lumen of block needles can measure needle tip pressure. Electrical impedance differentiates between intraneural and perineural needle tip placement. A new tip tracker needle has a piezo element embedded at its distal end that tracks the needle tip in-plane and out-of-plane as a blue/red or green circle depending on its relative location within the beam. Micro-ultrasound at the tip of the needle is in development. Early images using 40MHz in anaesthetised pigs reveal muscle striation, distinct epineurium and 30–40 fascicles > 75 micron in diameter. The next few years will see a technological revolution in tip-tracking technology that has the potential to improve patient safety and, in doing so, change practice.     

Microcomputer image processing in gastrointestinal endoscopy

A computer-based system was developed to handle information and endoscopic images in a clinical setting. The system is based on an 80286 AT computer whose topology includes a 16-bit color image capture/display graphics adapter and a 256 gray scale 8-bit digital image analysis processor. Using its color capabilities, one may initiate a picture database of patient's endoscopic images, x rays, and relevant clinical data. The computer-based imaging system allows instant access to this information and minimizes subjective evaluation, improving comparison and follow-up of treatments in a more objective manner. The image analysis components permit digital characterization of lesions, which allows online measurements and image enhancement. This is a cost-effective method of handling information and images in the clinical setting, facilitating endoscopic management and follow-up of the patient with gastrointestinal disease, as well as an effective research and teaching tool.     

The pulsed dye laser for fragmenting urinary calculi

The properties of a laser which effect stone fragmentation have been studied. The pulsed dye laser emitting at 504 nm. in one microsecond duration pulses appears to be the optimum out of a wide range of parameters tested. The laser is coupled to a 200 micron core fiber; this complete with its cladding has a total diameter of only 0.25 mm. Most calculi are fragmented by a series of pulses of up to 30 mJ. The system is used by firing bursts of pulses with the fiber actually in contact with the stone. The result is a very controlled fragmentation which is particularly suited to use in the confines of the ureter. This modality of treatment utilises less energy than ultrasound or electrohydraulic probes to fragment a stone and the very fine, flexible fiber represents a considerable miniaturization.     

Cell investigation into the biocompatibility of adult human dermal fibroblasts with PCL nanofibers/TiO2 nanotubes on the surface of Ti–30Ta alloy for biomedical applications

The polymer poly(ε-caprolactone) (PCL) has been used in the biomaterial field for its relatively inexpensive price and suitability for modification. Also, its chemical and biological properties are desirable for biomedical applications. The electrospinning process has been used for producing polymer fibers of PCL due in large part to an increased interest in nanoscale properties and technologies. Moreover, the use of biocompatible polymers for the viability of cell growth is a promising alternative to improve osseointegration. Characterization techniques such as scanning electron microscopy and contact angle were used for analyses of samples. Adult human dermal fibroblasts (neonatal) were utilized to evaluate the biocompatibility of the association of the electrospinning process of the biocompatible polymer (PCL) with TiO₂ nanotubes on the Ti–30Ta alloy surface. The results of this study showed a favorable response for adhesion on the surface. This promising material is due to the modulation of the biological response.     

Multichannel cochlear nucleus stimulation.

Stimulation of the cochlear nucleus (CN) has been used on a limited basis for rehabilitation of a select group of patients with bilateral acoustic neuromas. These patients were implanted with an electrode placed on the surface of the CN after resection of their tumors. Animal studies have demonstrated greater efficiency of a penetrating CN electrode in activating the central auditory system than a surface electrode. The objective of this work was to study the electrically evoked middle latency response generated by stimulation through a penetrating multichannel CN electrode in an animal model. Six pigmented guinea pigs underwent implantation with a penetrating multichannel CN electrode. Threshold, latency, and input-output functions of electrically evoked middle latency responses with different stimulation pads were studied. There were systematic differences in the latency and amplitude of the input-output functions depending on the site of stimulation within the CN. The results support the hypothesis that discrete activation of neuronal subpopulations within the CN is possible with a penetrating multichannel microelectrode.